Components & Versioning in .NET Core

Components

.NET Core consists of multiple components that are each versioned
independently and can often be mixed and matched.

The Shared Framework contains the APIs and the Virtual Machine and other runtime services needed for running .NET Core applications.

The current .NET Core Virtual Machine is called CoreCLR. This executes the .NET bytecode by compiling it JIT and provides various runtime services including a garbage collector. The complete source code for CoreCLR is available at https://github.com/dotnet/coreclr.

The .NET Core standard APIs are implemented in CoreFX. This provides implementations of all your favourite APIs such as System.Runtime, System.Theading and so on. The source code for CoreFX is available at https://github.com/dotnet/corefx.

The Host is also sometimes called the muxer or driver. This components represents the dotnet command and is responsible for deciding what happens next. The source for this is available at https://github.com/dotnet/core-setup.

The SDK consists of the various tools (dotnet subcommands) and their implementations that deal with building code. This includes handling the restoring of dependencies, compiling code, building binaries, producing packages and publishing standalone or framework dependent packages. The SDK itself consists of the CLI, which handles command line operations (at https://github.com/dotnet/cli) and various subprojects that implement the various operations the CLI needs to do.

Versions

Each of the components listed above are versioned separately. You can find out the version of each of those components.

For the SDK, you can use the --version option to dotnet to see the version. For example:

$ ~/dotnet-1.1.1/dotnet --version
1.0.0-preview2-1-003176

For the Host you can run dotnet by itself without any arguments or options to see the version.

For the Shared Framework there no command currently to display the version(s). I use ls /path/to/where/you/installed/dotnet/shared/Microsoft.NETCore.App which relies on internal implementation details. For example:

$ ls ~/dotnet-1.1.1/shared/Microsoft.NETCore.App/
1.1.1

Components in .NET Core Installations

Various official and unoffical packages, tarballs, zips and installers for .NET Core (including those available on https://dot.net/core) provide .NET Core in many variants. Two common ones are .NET Core SDK and .NET Core Runtimes. Each .NET Core SDK or .NET Core Runtime distribution contains a number (possibly 0) of hosts, sdk and shared framework components described above.

.NET Core Runtime contains

1 version of the Host

1 version of the Shared Framework

.NET Core SDK contains

1 or more versions of the Shared Framework (varies depending on the version of the version of the .NET Core SDK)

1 version of the Host

1 version of the SDK

Selecting Versions

It’s possible to have multiple .NET Core SDKs and .NET Core Runtimes available on disk. You can select the versions easily.

To select the version of the SDK to use, use global.json.

To select the version of the shared framework to use, use the .csproj file (or project.json if you are still using that).